Conductive screen and shield



April 29, 1930. E. o. SELBY -CONDUCTIVE SCREEN AND SHIELD Filed Nov. 24, 1928 Invntor .Eggene 0. Selby,

v His Attornqg Patented Apr. 29, 1930 UNITED 'STATESPATENT OFFICE mmmm o. SEL'BY, or sonENEc'rnnY, NEw- Yonx, AssreNon T GENERAL ELECTBIC:

COMPANY, A ooBronA'rroN on NEW YORK CONDUCTIVE SCREEN AND SHIELD Application filed November 24, 1928. Serial No. 321,708.

My invention relates to conductive screens and shields for preventing the electrical coupling which tends to exist between the input 7 I electric discharge device coupled with circuits in said compartments and to provide an opening for the device whereby it may stand ina normal operating position directly in the partition and between the compartments without disturbing the shielding or screening efiect of the partition between the compartments.

This type of shield is particularly adapted for use with screen grid type of electric dis- 26 char e devices in which a screen electrode or grid is located between a control grid or electrode and an anode for reducing the internal capacity of the device, that is, the control grid-anode capacity. In such devices the so leads and terminals for such electrodes are spaced as widely as possible, a known construction, being that in which the control grid terminal is at the top or one end of the enclosing bulb of the device and the anode terminal I 36 is at the base or epposite end thereof.

A screen embo ying the invention permits the operation of such devices. in a normal vertical position, with the grid or control terminal located in one compartment while I in the anode and remaining terminals at the base are located on the opposite side of the partition and in the other compartment.

My invention will ,bebetter understood however from the following description when 46 considered in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a diagrammatic representation of an electric discharge device andinput and output circuits therefor,

provided with a shield embodying the invention; Fig. 2 is a view in perspective on an enlarged scale showing the construction of a partition wall of the shield of Fig. 1 and the location of the electric discharge device there- 5 in; and Fig. 3 is a similar view of a modification.

Referring to Fig. 1, 5 is an electric discharge device of the shield-grid type having an anode 6, cathode 7, a control grid 8 and a shield grid 9 interposed between the anode and the control grid. Connected with the control grid is an input or grid circuit 10 in which is connected a tuning means comprising an inductance 11 and a variable tuning capacity 12 in shunt therewith. Signal voltageat the frequency to which'the tuning means is responsive is'appl ied to the control grid circuit 10 through suitable means connected with the inductance, which in this case is a signal voltage supply lead indicated at 13. Grid bias voltage is supplied to the grid circuit through a lead 14.

Operating voltages are applied to the anode, shieldgrid and cathode through suitable 76 leads 15, 16 and 17, and in the anode or output circuit 18 of the tube is located a tuning means comprising an inductance 19 and a variable tuning capacity 20. Voltages generated in.

the output or anode circuit across the tuning 30 means are conveyed to other suitable apparatus, not shown, through an output lead 21 and an isolating condenser or capacity 22.

The above-described circuits represent a common arrangement of input and-output g5 circuits for a screengrid tube when utilized as a radio frequency amplifier, and maybe taken as representing any electric discharge device having an input or control grid circuit and an output or anode circuit which are to be shielded from each other and-(from external electrical influences. y To shield the above-named circuits from external electrical influences a, conductive screen indicated at 23, preferably of sheet metal 96 such as copper or aluminum, is made to entirely enclose both the input'and output cir-" cuits and the device itself, and to shield the input and output circuits from each other 1, conducting partition: connected w1th and 100 I tween the input and the output circuits, as indicated at 24, so-that in the arrangement of the present example, the input orcontrol grid circuit is located in a compartment 25 within the screen, and the output or anode circuit is located in a compartment 26 within the screen.

In the usual screen of this character the walls and partition are vertical. It is also desirable to mount the electric discharge device in a vertical position. Furthermore, it is desirable to have the control grid and anode terminals of the devicein the same compartment with the circuit with which it is connected with suitable shielding about the terminals and internal elements of the tube or device.

To this end I so construct the partition between the compartments that the electric discharge device connected with the circuits in said compartments maybe located directly in the partition, whereby together with its terminals, it is properly shielded, and whereby its terminals are located in the "proper compartments Without interfering with the shielding provided by the partition between the input and output circuits in said compartments. 1

Referring now to Fig. 2 along with Fig.1, the construction'of partition 24 which provides this arrangement is shown more in detail. As shown in Fig. 2 the partition 24 is a plate out along a line 27 parallel with its top and bottom edges and pressedout or bent above and below the cut in opposite directions at substantially a right angle to the plane of the partition to form an opening which lies in a plane substantially at a right angle to the plane of the partition. and oppositely disposed recesses above and below the opening. The bends providing the recesses are preferably si-lbstanti'ally equal and may be considered to form a cylindrical enclosure 28, the-axis of which is substantially in the plane of the partition, whereby with a vertical partition, the tube maybe mounted within the enclosure in a corresponding vertical position with its axis parallel with the plane of the partition. -With a tube having its control grid terminal and anode terminal at op posite ends as'indicated at 29 and 30 respectively, the pressed out portions of the cylindrical enclosure form shields about said terminals and place these terminals in direct communication with the compartments in In constructing a partition of this charactype of partition may then be dropped in locate the cut at such a height above the base which their respective circuits are. located.

ter it is necessary to make it of such initial length that when out and pressed out to form acylindrical enclosure of the desired diameter, its shortened length is then sufficient to engage the opposite walls of the shield and contact therewith, whereby the construction of the shield is greatly simplified, since this or bottom edge that it will lie in a horizontal plane which will pass through the center of .the internal elements of the tube indicated at 31 of Fig. 2. \Vith this arrangement the lower portion of the tube and its terminals at the lower end are, in the example shown in Fig. 2', included in the compartment for the anode or output circuit While theupper part of the tube and the control grid terminal 30 are included in the compartment for the input or control grid circuit. -The partition then provides a shielding enclosure for the tube, an

effective shield between the compartments and an opening through which the tube may project between compartments. The opening is preferably of such size or diameter that at said opening the enclosures closely surround the tube; y

This arrangement is of very simple con struction, embodying merely a sheet of con-. ducting material, cut and bent in opposite directions above and below the cut and in efi'ect dropped in place about the tube in contact with the remainder of the shield. It is easily and cheaply manufactured and is easily and quickly mounted in place in the shield. It permits the tube to be mounted in the plane of the partition which is usually vertical and does not intierfere with the easy insertion and removal of the tube from its base or socket.

Referring now to Fig. 3 in Whichthe same reference numerals as used in Fig. 2 areused for corresponding parts, an annular ring 32 is shown between the tube and the cylindrical enclosure to shield the space between the tube and the shield at the cut 27. When provided with a flange 33, as shown in Fig. 3, which fits the enclosure and engages the walls thereof about the opening, this annular ring may be pressed in place about the tube to complete the isolation of the compartments separated by the partition. This annular ring is used when undesirable electrical coupling between the input and output circuits is extremely difficult to control, orin which. electrical coupling between such circuits would ordinarily be effected through the space about the tube within the cylindrical enclosure. In certain instances such as that in which the enclosure is only slightly larger than the tube the additional shielding ring may be unnecessary but in other instances, where it is used, it may be permanently secured in place by any suitable charge device including a, partition out along its length and bent in opposite directions to form an opening in the partition for permitting the projection of an electric discharge device therethrough with its axis substantially in the ,plane of the partition.

2. In a conductive screen for an electric discharge device, a partition cut along its length and bent on either side of the cut in opposite directions to forman opening for an electric discharge device, said opening being in a plane at a rightangle to the plane of the partition. I i A 3. In a conductive screen for electric discharge apparatus, a partition out along its length and bent on either side of the cut in opposite. directiohs to form recesses substantially equal and semi-cylindrical in form. 4. A- artition wall forming a'conductive g9 screen or an electric discharge device and comprising a conductive plate having an opening and a pair of oppositely disposed recesses located respective y above and below said opening, said opening being in a plane at substantially a right angle to the plane of the plate. I

5. A partitionwall forming a conductive screen for an electric discharge device and comprising a conductive plate having an so opening and a pair of oppositelyidisposed recesses located res ctlve y above and below said opening, an an annular ring located in said opening and engaging the inner walls of said recesses about said opening. as 6. In conductive screen, a vertical part tionwall cut along its length between its top and bottom edges and bent above and below the cut in opposite directions to form an opening in which an electric discharge device may stand with its terminals on opposite sides of the partition, the plane of said opening being at substantially a right angle to the plane of partition and at a level such that it intersects the internal structure ofthe electric discharge device midway ofits length when standing in said opening.

7. In a conductive screen, a partition wall cut along its length and bent on either side of the cut in opposite directions, to form an i opening between two semi;cylindrical opp0-' sitely disposedrecesses about a common axis which lies substantially in the plane of the partition wall, and a flanged annular rmg which engages ,the interior walls of said recesses within said opening.

. In witness whereof, I have hereunto set my hand this 23rd day of November, 1928.

EUGENE O. SELBY. 

